Sylvania



(No Model.)

0. STEFPEN. PROCESS OF OBTAINING SUGAR.

N0. 489,879. Patented Jan. 10,1893

jar/@7672 NTED STATES PATENT FFICE.

CARL STEFFEN, OF VIENNA, AUSTRIA-HUNGARY, ASSIGNOR, BY MESNEASSIGNMENTS, SYLVANIA.

TO W'ILLIAM W. FRAZIER, OF PHILADELPHIA, PENN- PROCESS OF OBTAININGSUGAR.

SPECIFICATION forming part of Letters Patent No. 489,879, dated January10, 1893.

Applicationfiled November 20,1890. Serial No. 372.110. (N0 specimens.)Patented in Germany February 27.1890, No. 58,191;

in France March 4,1890,No.204=,121; in England March 6, 1890, No. 3,589;in Belgium March 6,1890,1 To. 89,737 and in Spain March 10, 1890,110.10,595.

To all whom it may concern:

Be it known that I, CARL STEB'F'EN, engineer, a subject of the Emperorof Austria-Hungary, and a resident of Vienna, Austria-Hungary, haveinvented certain Improvements in the Art of Extracting OrystallizableSugar from Saccharine Substances, (for which I have been granted patentsin England, No. 3,589, dated March 6, 1890; in France, No. 204,121,dated March 4:, 1890; in Belgium, No. 89,737, dated March 6, 1890; inSpain, No. 10,595, dated March 10, 1890; and in Germany No. 58,191,dated February 27, 1890;) of which the following is a specification.

My invention relates to an improved process for obtaining fromsaccharine juices of plants, and from other more or less pure saccharinesolutions the crystallizable sugar which they may contain, by firstusing such juices or solutions, to wash raw sugar or masse-cuite, andafterward subjecting them to a novel method of boiling in order toproduce sugar crystals. In the present and customary method of boilingsuch juices and solutions, the liquor is from time to time introducedinto the pan as the evaporation proceeds, and the portion of liquorintroduced is usually of the same degree of purity, from thecommencement to the close of the operation. As the sugar separates aportion is deposited on the crystals first formed thus determining theirgrowth, and another portion gives rise to the formation of new crystals.During the evaporation, therefore, the sugar assumes a solid orcrystalline form while the impurities accumulate in the mother liquorwhich thus consequently decreases in purity or amount of crystallizablesugar. The

decrease is not. however, a steady or continu-- one one, as each time afresh quantity of liquor is fed into the pan the purity of its liquidcontents is, for the time being increased. It results in consequence,that in this method of boiling, mother-liquor is not able to give up itsmaximum of crystallizable sugar as rapidly as it should do, nor is theenergy of crystallization for a given period of time able to reach amaximum.

In the accompanying drawingsz-Figure 1,

is a diagram, is given to illustrate the progress of crystallization andevaporation, in the method of extracting crystallizable sugar,heretofore in use. Fig. 2, is a similar diagram, in like mannerillustrating the progressive action and conditions at different periodsin the process of reduction, according to my improved method.

In Fig. 1, the vertical lines or ordinates are equally divided by thehorizontal lines representing abscissas.

The diagonal line in Fig. 1, shows the condition of the liquid contentsof the vacuum pan during the progress of evaporation andcrystallization. The ordinates represent the coeflicient of purity ofthe liquor, and the abscissas the time, the boiling has been inprogress. The abscissas are divided in spaces representing ten minuteseach. (The term coefficient of purity is here used in the sense in whichit is generally employed: thus the statement that a liquor has acoefficient of purity ninety, is equivalent to saying that ninety percent. of the total solid matter present in solution is crystallizablesugar. This formof expression deals only with the quality of thesolution, and gives no information regarding its strength or in otherwords as to the proportion of water present.)

The curves 0, show the periodical increase in purity of the motherliquor brought about by the introduction from time to time of freshliquor, in the usual way. This mother liquor owing to theperiodicalimprovement, is unable to reach in a given period of time itslowest possible degree of purity by the separation of sugar. To reachthis lowest possible degree of purityis the object and ultimatum of theboiling process.

In the process of boiling it is necessary that the fluid character ofthe mass be not diminished by evaporation beyond the point at which theparticles of crystallizable sugar move easily in it to form crystals orto attach themselves to crystals already formed, or below the point atwhich the contents of the vacuum pan may be easily withdrawn. As sugarboiling is now practiced this limit of evaporation is reached while yeta large protrue molasses because of this undue amount of sugar. Theboiling of such mother-liquor or sirups as they are technically called,is however, frequently a matter of considerable difficulty; and beforethe available sugar can be completely extracted the operation may haveto be repeated several times.

Boiling in vacuum premises that the liquor or siru p shall possess suchcrystallizin g capacity that grains of sugar can be produced; but theease and rapidity with which the crystals are formed dependslargely uponthe character and purity of the solution to be evaporated. Theseparation of crystals having however once commenced, takes placesubsequently with greater ease; as those first formed promotecrystallization by their presence, by the influence which they exertupon the sugar still in solution. Consequently, the larger the number ofcrystals present, the more energetic will be the crystallization. Veryimpure solutions cannot be boiled to a grain under ordinarycircumstances, because the grain refuses to form at first and theconditions then rapidly become less favorable for crystallization owingto the increase in viscosity of the solution. In considering thisquestion, it should therefore be borne in mind that the evaporation ofsaturated sugar solutions is not of necessity accompanied bycrystallization, and this is especially the case with very impure sugarsolutions; these readily become supersaturated. It has, however, longbeen known that if such impure solutions are brought in contact with asufficiently large number of crystals, a very effective crystallizationcan be brought about in the vacuum pan; and this knowledge has been madepractical use of in sugar factories by the addition of raw sugarcrystals to j uices which could otherwise only be boiled with greatdifficulty. Similarly it is sometimes customary in sugar refineries,when very small crystals are desired, to bring the liquor to thecrystallizing point, and then by theintroduction of a quantity of finelypulverized sugar to start energetic crystallization, thus insuring theformation of small crystals by shortening the time of boiling andconsequently that given to the crystals in which to grow. I

It is to be inferred from an inspection of the curve 0, in Fig. 1,thatthe process of boiling would be more correctly carried out, and wouldalso be more effective, if mother-liquor were not subject to periodicalimprovement. It 011 the other hand the liquor drawn from time to timeinto the pan were to correspond in purity with that of the liquorcontents of the pan for the time being, a mother liquor of much greaterimpurity and consequently much more exhausted of its sugar would beobtained in a given time. The object among others, of the processforming the subject matter of this application, is to produce fromliquor, or sugar solutions in general, in the manner given below, aseries of solutions ranging from a very low to a very high degree ofpurity. The total quantity of liquor thus operated upon should be aboutsufficient for a pan of sugar.

In my method, when the liquor has been prepared in portions ofincreasing purity, the boiling operation is commenced with the best orpurest portion. This, in consequence of its purity, possesses greatcrystallizing power; and it results that in the shortest possible time,and under the most favorable possible conditions sugar crystals areformed in great number. As the evaporation proceeds the remainingportions of liquor are drawn into the pan in order of their purity, themost impure being consequently left to the last. It is clear from whathas been already said,that the crystals first formed are able to promotethe separation of crystals from. the less pure portions of liquorsubsequently admitted to the pan and consequently the last and veryimpure portions, which would under other circumstances crystallize withthe greatest of difficulty, yield their sugar readily under theinfluence of the large number of sugar crystals present. It is moreoverevident that, as each successive portion of liquor is drawn into thepan, the quantityof sugar present in a crystalline condition hasincreased, and consequently the influence it exerts upon each succeedingportion increases also; so that the constantly increasing effect of thegreater impurity of the last portions in retarding crystallization iscounterbalanced by the constantly increasing quantity of the sugarpresent which promotes it. In consequence of the attractive action thusexerted by the crystals the whole of the sugar capable of crystallizingis obtained in a solid form, and the mother-liquor remaining is truemolasses.

The process has still other advantages.

The quality of the mother-liquor is at no time suddenly improved, as theportions of liquor successively introduced into the pan areapproximately the same in quality as the mother-liquor surrounding thecrystals at the time of such introduction. The addition therefore, ofeach succeeding portion merely increases the quantity of themother-liquor without materially affecting its quality. It results thatthe liquor is more completely under the control of the boiler, who,under other circumstances frequently has difficulty in preventing theformation of crystals he does not desire. It is moreover often a matterof considerable importance that the crystals should be regular in form,as well as in size, and this end can be best attained by preventing anysudden variation in the character of the mother-liquor. The formation ofsmall crystals toward the end of the operation is also entirely obviatedfor the reason that owing to the last portions of liquor being veryimpure, they possess buta very small tendency to deposit new crystals.The separation of sugar as does occur being essentially brought about bythe influence of crystals already present, with the result that thesugar is deposited upon them, merely increasing their size but not theirnumber. In Fig. 2,the same system of lines is shown representingordinates and abscissas with difference only in number, the degrees ofpurity ranging from sixty-five to one hundred.

In Fig. 2, the curve B, represents the condition of the Inother-liquorduring the course of evaporation and crystallization in vacuum, when theliquor fed into the pan is of the same degree of purity throughout theoperation. The ordinates give the quotient of purity of themother-liquor, the abscissas the time of duration of the boiling. Thecurve A, in the same figure shows the condition of another mother-liquoralso during crystallization and evaporation, but in this case the liquorfed into the pan is divided into portions according to quality. Theportions form collectively a series of sirups increas ing gradually froma very low to a very high degree of purity; and are taken in properorder into the pan commencing with the solution of highest value, andending with that of greatest impurity. The ordinated in this case alsodenote the quotient of purity of the mother-liquor, and the abscissasthe time of duration of the boiling.

The numerical figures given for the co-ordinates are those obtained byactual experiment; they show that in the method of boiling lastdescribed a mother-liquor of considerably less purity can be withdrawnfrom the crystallizingprocess in a given time than when the method ofboiling first given is followed.

This is due to two principal causesz-First. By commencing the boilingoperation with a liquor of great puritya large quantity of crystals isformed in the shortest possible time, and these crystals promote theseparation of sugar from the liquor of less purity which follow. Second.The liquor drawn into the pan does not materially improve the quality ofmother-liquor but merely increases its volume, and upon evaporation moresugar is deposited, and a mother liquor of lower quality produced, whichis in turn increased in quantity by the addition of liquor of likevalue.

Having now fully described in the foregoing my new method of boilingliquor after the same has been prepared in portions of as cendingpurity,l will proceed to discuss the preparation of such portions ofliquor from subsequently employed; and which will consequently be unableto dissolve any sugar when brought in contact with it at thattemperature. The liquor thus prepared is then employed as a lixiviatingfluid to displace the molasses from a masse-cuite obtained in apreceding boiling operation, and when the n10- lasses has beencompletely expelled, the liquor adhering to the crystals is in turndisplaced by the use of steam, water, or a more or less completelysaturated solution of pure sugar.

By proceeding in the manner described, the liquid first flowing from themasse-cuite will consist essentially of molasses, which at the time ofcommencing the washing operation was surrounding the crystals of themassecuite. The liquid following however will gradually increase inpurity, owing to the admixture of a portion of the liquor used forlixiviating with a portion of the molasses, and this increase in puritywill continue until the whole of the molasses has been expelled, whenthe liquor will flow from the sugar crystals in precisely the samecondition as it was admitted to them. As the liquor is followed by apure solution of sugar, the liquid flowing from the sugar crystals willgradually approach to, and finally reach, a condition of absolute p11-rity.

In the case in which steam or water is employed to displace the liquor,some of the washed sugar crystals are dissolved, and thus a solution ofpure sugar is formed which displaces the liquor adhering to thecrystals. remaining undissolved.

After discarding the first portions expelled from the masse-cuite whichconsists essentially of molasses, the solution is collected in portionsof increasing value which range from a very low to a very high degree ofpurity. The liquor so collected is then subjected to the boiling processabove described, and a masse-cuite is obtained, containing in a solidform the whole of the sugar capable of crystallizing originally presentin the liquor.

By submitting the masse-cuite to the washing process in the mannerdescribed it can be entirely free from molasses and the whole of thesugar obtained in a condition of great purity. It is thus possible toobtain in a pure form, from a given liquor, the whole of the sugarcapable of crystallizing by first using such liquor forwashingamasse-cuite obtained in a preceding operation, and then subjecting thesame divided into portions according to purity, to the boiling processin the manner described.

The process may be carried out in practice in the following manner:-Thej uices of plants, or solutions of sugars, are just sufticientlyconcentrated in the ordinary evaporating apparatus, to convert them intosaturated solutions of sugar. If it is not desired to work warm, but atordinary temperatures, the solutions may be cooled by the help of any ofthe appliances usually employed. Massecuite from a preceding boilingoperation, either in a warm condition or after passing through one ofthe refrigerators ordinarily used for the purpose, is filled in thesuction vessels, subjected to suction, and lixiviated by means of asaturated solution prepared as above described. The molasses drawn offby means of a pump, through the perforated bottoms of the suctionvessels, is discarded; and the lixiviating fluid is then delivered intoa number of reservoirs which separate the same into portions ofdifferent quality. The flow of liquor to the sugaris continued until afluid passes from the suction vessels of nearly the same degree ofpurity as that entering them. A saturated solution of pure sugar is thenfed into the suction vessels until it is withdrawn from them by the pumpalmost unchanged. The crystals are not surrounded by a pure solution ofsugar, and can be simply dried or melted and converted into any desiredform of refined sugar. The entire washing fluid, which is almost equalin quantity to that from which the masse-cuite was produced, being nowseparated according to its quality in the reservoirs, is from theretaken to the vacuum pan and crystallized in order of decreasingpurity.The masse-cuite produced is then treated with a fresh quantity ofsaturated liquor so thatit may be resolved into pure sugar on the onehand, and on the other into molasses absolutely free from sugar capableof crystallizing.

The separation of the molasses, the washing with liquor and thesubsequent liXiviation with water or steam (if employed) can beaccomplished in centrifugal machines; and in this case also, after themolasses has been discarded, the liquid discharge from the machines isseparated in a sufficiently large number of portions according to itsquality. It is recommended that not less than ten portions of liquor ofvarying quality be employed,

and when the best effect is looked for it is even desirable that thenumber should be larger if possible.

If it is necessary to use the entire quantity of liquor required for oneboiling operation, for the washing process, the surplus is to be addedto that quantity of liquor having the same degree of purity as itself,and is not to be taken to'the pan until all portions of liquor ofgreater purity have preceded it.

What I claim and desire to secure by Letters Patent is:

1. The process of extractingsugar from the juices of plants andsolutions of sugar in general, by the successive introduction of sugarsolutions of constantly decreasing purity into the vacuum apparatus forevaporation and crystallization, such solutions being prepared byemploying a saturated solution of more or less pure sugar to expel thesirup from a masse-cuite in the manner herein described, and collectingthe liquid flowing therefrom into a number of portions of ascendingpurity.

2. The herein described process of extracting sugar from sugar solutionsby systematic boiling, which consists in ad ding to a solution of sugarundergoing evaporation and crystallization, and consequently still incontact with the crystals it has deposited, solutions of sugarsuccessively decreasing in purity, but of approximately the same qualityas the liquor in process of crystallization at the time such addition ismade.

In witness whereof I have hereunto signed my name in the presence of twosubscribing Witnesses.

CARL STEFFEN.

Witnesses:

W. B. MURPHY, J OHN I'I. FORSTER.

